The present invention relates to a method for disconnecting a connection of a subscriber station in a mobile communication system comprising a mobile services switching centre and a visitor location register, which keeps a record of subscriber stations located in the coverage area of said mobile services switching centre. The invention further relates to a mobile communication system comprising: a mobile services switching centre and a visitor location register, information on subscriber stations located in the coverage area of said mobile services switching centre being stored in the visitor location register, and a home location register, information on particular subscriber stations being stored therein, and comprising means for transmitting a cancellation message to said visitor location register for removing the subscriber information on a particular subscriber station from the visitor location register.
The present invention particularly relates to a mobile communication system of the GSM (Global System for Mobile Communications) kind, in which system the subscriber information on a particular mobile station is stored both in the mobile station""s unique home location register (HLR) and in the visitor location register (VLR) of the mobile services switching centre in whose coverage area the mobile station is located at the particular moment. The concept xe2x80x98coverage area of a mobile services switching centrexe2x80x99 herein refers to the geographical area which the mobile services switching centre in question serves via base stations and other network elements.
When a mobile station moves between the coverage areas of different mobile services switching centres, for instance, it becomes necessary to remove the subscriber information on the mobile station from the visitor location register corresponding to the mobile services switching centre whose coverage area the mobile station has left. In a GSM system, for instance, this can take place in such a manner that the home location register of the mobile station, which receives the information that the mobile station is located in the coverage area of a new mobile services switching centre, transmits a cancellation message to the visitor location register corresponding to the mobile services switching centre whose coverage area the mobile station has left. This removal of mobile station subscriber information from the visitor location register can be utilized also in other contexts, for example when a mobile station is completely closed (i.e. it is prevented from being used in a mobile communication system) or when the mobility of a mobile station is restricted for instance such that the mobile station is prevented from being used in the coverage area of a certain mobile services switching centre. In the last two cases, the operator can, via an interface, direct the mobile station""s home location register to transmit a cancellation message to the visitor location register.
A disadvantage of the known solution described above is, however, that in some cases, to remove subscriber information from a visitor location register is not a sufficient procedure since the removal does not prevent the mobile station from continuing an ongoing connection it has at the removal moment. Removing the mobile station subscriber information from the visitor location register does not prevent the mobile station from, for instance, continuing an ongoing call at the removal moment; instead, the call continues as long as the user of the mobile station desires. This is an extremely unpleasant situation to the operator for instance when the operator would like to prevent the mobile station from incurring further costs or immediately prevent the mobile station from being used in the coverage area of a particular mobile services switching centre.
An object of the present invention is to solve the problem described above and to achieve a solution for disconnecting a connection of a particular subscriber station, i.e. a mobile station as efficiently and easily as possible, and for preventing, even more efficiently, a mobile station to be closed from incurring further costs after it has been closed. This object can be achieved by the method of the invention, characterized by comprising the steps of: arranging in said visitor location register disconnection means for transmitting a disconnection message to the mobile services switching centre corresponding to the visitor location register, and directing the disconnection means of the visitor location register to transmit the disconnection message to said mobile services switching centre for disconnecting an ongoing connection of a particular subscriber station.
The invention further relates to a mobile communication system to which the method of the invention can be applied. The mobile communication system of the invention is characterized by the visitor location register comprising disconnection means for transmitting a predetermined disconnection message to the mobile services switching centre, and the mobile services switching centre comprising means for disconnecting an ongoing connection of the subscriber station in response to said disconnection message.
The invention is based on the idea that to disconnect connections of a particular subscriber station becomes easier and more efficient when a visitor location register is equipped with means by which it is able, if necessary, to direct a mobile services switching centre to disconnect an ongoing connection of a particular subscriber station. Consequently, an ongoing connection from the mobile station can be immediately disconnected at any moment chosen by the operator.
Hence, the most significant advantages of the method and system of the invention are that the invention enables the operator to immediately disconnect a connection of a mobile station at any moment desired by the operator, whereby the mobile station avoids incurring further costs, and that the invention can be applied also to existing mobile communication systems after slight modifications since necessary modifications can be performed by software.
In a preferred embodiment of the system in accordance with the invention, only a single procedure is required from the home location register to close a particular subscriber station and to disconnect its connections. This can be achieved by adding means to the home location register by which it is able to transmit a cancellation request that includes a disconnection command to the visitor location register when the operator, for instance, removes the subscriber information on a particular subscriber from the home location register. To apply this embodiment of the present invention requires both the home location register and the visitor location register to be able to process (HLR to transmit and VLR to receive) the cancellation message that includes the disconnection command.
In another preferred embodiment of the system of the invention, parameter conditions can be stored in a visitor location register, the parameter conditions indicating how the visitor location register should operate when it receives a cancellation message. This embodiment of the invention enables the operator to determine case by case when a connection of a particular mobile station should be disconnected in connection with a received cancellation message, and when not. In other words, the visitor location register operator can determine, for example by the parameter conditions, that the visitor location register transmits a disconnection message to the mobile services switching centre whenever it receives a cancellation message originating from another operator""s home location register. The advantage of this is that the connection of the mobile station can be disconnected also in situations in which the home location register of the mobile station is unable to add the disconnection command to the cancellation message.
The preferred embodiments of the method and mobile communication system of the invention are disclosed in the attached claims.